In recent years, an interest in the development of eco-friendly energy has increased. A pure electric vehicle using a battery as an energy source, an engine hybrid electric vehicle and a fuel cell hybrid electric vehicle using the battery as an energy buffer, and the like, have also been intensively developed in the vehicle field.
In the hybrid vehicle described above, a battery system is one of the main components in determining a quality or utility of the vehicle. The battery system of the hybrid vehicle is an energy source of the vehicle that assists in an output of an engine during driving of the vehicle or in accumulating generated energy therein, and a technology for controlling and monitoring the battery system is important.
Technologies for controlling the battery system include a power controlling technology, a cooling technology, a diagnosing technology, a technology of estimating a state of charge (SOC) of a battery, and the like. Among them, the technology of estimating an SOC of a battery is directly used for the purpose of determining a driving strategy of the vehicle.
In addition, in the hybrid vehicle, the SOC of the battery is calculated to control charging and discharging of the battery, thereby making it possible to improve operational efficiency of the vehicle.
In addition, the battery becomes deteriorated depending on a use environment or a use period, such that an available capacity of the battery is decreased or a resistance of the battery is increased. Therefore, a state of health (hereinafter, referred to as a ‘SOH’), which is a performance of the battery, is deteriorated as compared with that of a newer battery.
That is, a current battery system performs the charging or the discharging on the basis of only an estimated SOC and a voltage of the battery, and thus, a technology for limiting a use range, an output, or the like, of the battery depending on a deterioration state of the battery is needed.